Polyurethanes based on three-component polyester oligomers



United States Patent n- 3,535,287 Patented Oct. 20, 1970 US. Cl. 260-759 Claims ABSTRACT OF THE DISCLOSURE Curable, hydroxyl terminatedpolyester oligomers have been prepared by the interaction of an esterdiol, a polyol selected from the group consisting of 1,1,l-trimethylolpropane and pentaerythritol and an ester form ing compound such as adiaryl carbonate, phosgene or a cyclic dibasic acid or acid anhydride.

This is a division of application Ser. No. 461,175, filed June 3, 1965,now US. Pat. No. 3,449,467. These oligomers are cured withpolyisocyanate curing agents.

This invention relates to hydroxyl terminated polyester oligomers andparticularly to those which are curable to hardened coatingcompositions.

There is a continuing need for curable resins to be used in compositionswhich after application to a substrate and curing thereon provideweather-resistant surface coatings. In order to resist discolorationupon aging such resins when cured should be transparent to ultravioletlight. The cured resins should also be tough, flexible and exhibit highimpact strength. Since coating resins are conventionally applied in asolvent system the uncured resin should remain soluble in the coatingsolvent and not crystallize out of solution.

Such a resin has been prepared which is a curable, hydroxyl terminatedpolyester oligomer obtained by the interaction of:

(a) A diol having the general formula:

wherein each of R and R is an alkyl group having up to 10 carbon atomsand n has a value of to l;

(b) a polyol selected from the group consisting of 1,1,1-

trimethylol propane and pentaerythritol; and

(c) an ester forming compound selected from the group consisting ofdiaryl carbonates, phosgene, and a cyclic dibasic acid or anhydridethereof. Examples of alkyl groups which can represent R or R is the diolhaving the formula wherein R, R and n are as defined above, include:methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tbutyl, and thelike. In one preferred embodiment R and R are methyl and 11:0 in whichcase the diol is neopentyl glycol. In another preferred embodiment R andR are both methyl and 11:1 in which case the diol is an ester-diol. Thisester-diol can be prepared according to methods described in U.S.2,811,562 and US. 3,057,911.

The polyols used in this invention, 1,1,1-trimethylol propane orpentaerythritol are commercially available.

The preferred diaryl carbonate is diphenyl carbonate althoughsubstituted diphenyl and dinaphthyl carbonates can be used if desired.

The cyclic dibasic acids or anhydrides which can be used includearomatic diacids or dianhydrides such as phthalic anhydride, isophthalicacid and the like as well as their halogen or alkyl substitutedderivatives and cycloaliphatic dianhydrides such as A-tetrahydrophthalic anhydride, hexahydrophthalic anhydride, chlorendicanhydride and the like.

The hydroxyl terminated polyester oligomers are prepared by acondensation polymerization process which affords a very complex mixtureof oligomers having different hydroxyl contents, hydroxylfunctionalities, molecular weights, and branch contents with the averagevalues of those parameters determined by the molar ratio of reactants.One preferred oligomer arises when 1,1,1- trimethylol propane,neopentylglycol and diphenyl carbonate are interacted in a charge molarratio of 2/ 7.7/9. It is believed that such an oligomer has a hydroxylfunctionality of 4.9, a molecular weight of about 1900, and

repeating units.

Hydroxyl functionality is defined for the purposes of this invention asthe number of hydroxyl groups per molecule. Obviously, many othercombinations of molar ratios can be used and these also afford oligomersuseful for coating resins. However, a definite formula cannot beascribed to these oligomers because their exact structure cannot beascertained. Analytical techniques reveal some of their physicalconstants and functional groups and so permit stoichiometry calculationsfor determining amounts of curing agents to employ in curingformulations but this is not a revelation of molecular architecture orstructure.

Other preferred oligomers arise from the interaction of1,1,1-trimethylol propane, ester-diol, and diphenyl carbonate in moleratios of about 2/ 3.7-4.4/ 5-5 .7. Other mole ratios can be used ifdesired.

Still other preferred oligomers include those obtained by theinteraction of 1,1,1-trimethylol propane, esterdiol or neopentyl glycoland a dianhydride such as phthalic, isophthalic, tetrahydrophthalic orhexahydrophthalic anhydride in a mole ratio of about 2/2.73.7/4-6. Otherratios including substitution of pentaerythritol for 1,1,1-trimethylolpropane can also be used.

Conventional reactors and vacuum distillation equipment can be used forthe preparation of the oligomers. In those condensations where a diarylcarbonate is the esterforming reactant, phenol is a byproduct and itsremoval is best efiected with a fractionating column having at least 10theoretical plates. Where a dianhydride is the ester-forming reactant aDean-Stark trap or Weir box facilitates removing the Water in azeotropicdistillation.

The temperature range preferred for the preparation of the oligomers isabout 175 to 200 C. although a range of about 150 to 250 C. can also beused if desired.

Pressure is not narrowly critical but subatmospheric pressures of about20 to 150 mm. are preferred, in preparations utilizing a diarylcarbonate as the ester-forming reactant. Atmospheric pressureesterifications can be used with the dianhydride reactants.

Time of reaction is not narrowly critical for the oligomer preparationbut for efiiciency and economical yields at least 2 hours should beused. The upper limit is determined by the kinetics of the particularcondensation and the degree of conversion desired but is not critical.

The curable hydroxyl terminated polyester oligomers of the invention canbe cured or hardened with crosslinking agents such as the polymethylethers of polymethylol melamines and polyisocyanates.

Hexamethoxymethylmelamine is the preferred polymethylolmelamine in thisinvention although others can be used. Hexamethoxymethylmelamine isreadily soluble in water, low molecular weight alcohols, and phenols,sparingly soluble in low molecular weight ketones, esters, nitromethaneand similar polar solvents. It is substantially insoluble inhydrocarbons, halogenated hydrocarbons and silimar nonpolar solvents.Solvents such as aromatic hydrocarbons, however, readily dissolve thecombination of hydroxy-terminated oligomer andhexamethoxymethylmelamine. Hexamethoxymethylmelamine can be representedby the formula:

1T (CH2O CHa)2 It is preferred to employ an acid catalyst with thehexamethoxymethylmelamine crosslinking agent such as p-toluene sulfonicacid, phosphoric acid, a sulfonic acid or the like.

The polymethyl ethers of polymethylol melamines are well known in theart as are methods for preparing them. Reference is made to U.S.3,065,109 which discloses their preparation. Polymethylol melamines canbe prepared by reacting one mol of melamine with at least two mols offormaldehyde. A fully methylolated melamine, such ashexamethylolmelamine, can be prepared by reacting at least six mols offormaldehyde with one mole of melamine. In order to obtain the desiredmethyl ether, the polymethylol melamines thus produced are reacted withthe requisite amount of methylol under conditions of mineral acidcatalysis. Thus, for example, reacting two mols of methanol with one molof a dimethylolmelamine results in the formation of the dimethyl etherof dimethylolrnelamine. Higher methylolmelamines can be reacted withfrom two to six mols of methanol as determined by the number ofavailable methylol groups and the degree of etherification desired. Fohexample, starting with tetramethylolmelamine, it is possible to preparethe dimethyl ether and the tetramethyl ether. It is also possible toproduce, as a further illustration, a trimethyl and pentamethyl ether ofhexamethylol melamine. Upon complete etherification ofhexamethylolmelamine, the hexamethyl ether or hexamethoxymethylmelamineis produced.

The polyisocyanates used in this invention are organic polyisocyanatescontaining two or more isocyanate groups. These organic polyisocyanatescan be alkyl, cycloalkyl, aryl, aralkyl or alkaryl polyisocyanates. Itis preferred to use diisocyanates although triisocyanates or higherpolyisocyanates can also be used, if desired. Preferred isocyanatesinclude bis(2-isocyanatoethyl)carbonate (CDI),

bis(2-isocyanatoethyl)-4-cylohexene-1,2-dicarboxylate (CEDI),

bis(2-isocyanatoethyl)fumarate (FDI),

bis(2-isocyanatoethyl)-1,4,5,6,7,7-hexachloro-5-norbornene-2,3-dicarboxylate (HEDI),

methylene bis(4-phenyl isocyanate) (MDI),

bis(2-isocyanatoethyl)-5-norbornene-Z,3-dicarboxylate (NEDI) and2,4-tolylenediisocyanate (TDI).

As examples of other suitable polyisocyanates which are employed hereincan be mentioned 1,2-diisocyanatoethane, 1,3-diisocyanatopropane,1,2-diisocyanatopropane, 1,4-diisocyanatobutane,1,5-diisocyanatopentane, 1,6-diisocyanatohexane,bis(3-isocyanatopropyl)ether, bis(3-isocyanatopropyl)sulfide,1,7-diis0cyanatoheptane, 1,S-diisocyanato-2,Z-dimethylpentane,1,6-diisocyanato-3-methoxyhexane, 1,8-diisocyanatooctane,1,5-diisocyanato-Z,2,4-trimethylpentane, 1,9-diisocyanatononane,1,lO-diisocyanatodecane, 1,6-diisocyanate-3-butoxyhexane,

the bis(3-isocyanatopropyl)ether of 1,4-butyleneglycol,1,1l-diisocyanatoundecane, 1,l2-diisocyanatododecane,bis(isocyanatohexyl)sulfide, 1,4-diisocyanatobenzene, 2,4-diiso cyanato-1-chlorobenzene, 2,4-diisocyanato-1-nitrobenzene, 2,5-diisocyanato-1-nitrobenzene, 3,6-diisocyanato-1,4-dichlorobenzene, 2,5-diisocyanato-1-chloro-4-methoxybenzene, 2,5-diisocyanato-l-methoxybenzene, 2,4-diisocyanato- 1 -methoxybenzene, 2,5-diisocyanato-1-methyl-4-methoxybenzene, 2,4-diisocyanatol-ethylbenzene,2,4-diisocyanato-1-ethoxybenzene, 4,6-diisocyanato-1,3-dimethoxybenzene,2,5 -diisocyanato- 1 ,4-dimethoxybenzene,2,4-diisocyanato-1-propylbenzene, 2,5-diisocyanato-l-propylbenzene,2,4-diisocyanato-1-isobutylbenzene, 2,4-diisocyan ato- 1-isobutoxybenzene, 2,5 -diisocyanato-1,4-diethoxybenzene,1,3-diisocyanatocyclohexane, 1,4-diisocyanatocyclohexane, 1,4-diisocyanatonaphthalene, 1,5 -diisocyanatonaphthalene,2,6-diisocyanatonaphthalene, 2,7-diisocyanatonaphthalene,1-(isocyanatomethyl)-2-(3-isocyanatopropyl)-3,5-

dimethylcyclohexane, 1, 3-bis(4-isocyanatophenyD-propane,a,B-bis(2-isocyanatoethyl)-9, IO-endoethylene dihydroanthracene,2,4-diisocyanatol-methylcyclohexane,2,4-diisocyanato-l-ethylcyclohexane, bis(4-isocyanatocyclohexyl)methane,1,1-bis(4-isocyanatocyclohexyDethane,2,2-bis(4-isocyanatocyclohexyD-propane,bis(2-methyl-4-isocyanatohexyl)methane,bis(3,5-dimethyl-4-isocyanatohexyDmethane, 1-isocyanatomethyl-4-isocyanatobenzene, 1-(2-isocyanatoethyl)-4-isocyanatobenzene,

1-(2-isocyanatoethyl)-3-isocyanatobenzene,

1-(3-isocyanatopropyl)-4-isocyanatobenzene,

1-(4-isocyanatobutyl)-4-isocyanatobenzene,

1,5-diisocyanatotetrahydronaphthalene,

4,4-diisocyanatoazobenzene,

2-methyl-4,4'-diisocyanatoazobenzene,

4,4-diisocyanato-1-naphthaleneazeobenzene,

2,4-diisocyanatodiphenylether,

dianisidene diisocyanate,

ethylene glycol bis(4-isocyanatophenyl)ether,

diethylene glycol bis(4-isocyanatophenyl)ether,

2,2'-diisocyanatobiphenyl,

2,4-diisocyanatobiphenyl,

4,4-diisocyanatobiphenyl,

3,3'-dimethoxy-4,4-diisocyanatobiphenyl,

3,3'-dimethyl-4,4-diisocyanatobiphenyl,

3,3-dimethyl-4,4'-diisocyanatobiphenyl,

2-nitro-4,4-diisocyanatobiphenyl,

bis(4-isocyanatophenyl)methane,

bis(2-methyl-4-isocyanatophenyDmethane,

2,2-bis(4-isocyanatophenyl)propane,

bis(2,5-dimethyl-4-isocyanatophenyDmethane,

cyclohexyl-bis(4-isocyanatophenyl)methane,

bis(3-methoxy-4-isocyanatophenyl)methane,

bis(4-methoxy-3-isocyanatophenyDmethane,

bis(2-methyl-5-methoxy-4-isocyanatophenyDmethane,

2,2-bis(3-chloro-4-isocyanatophenyDpropane,

2,2'-diisocyanatobenzophenone,

2,4-diisocyanatodibenzyl,

p-nitrophenyl-bis (4-isocyanatophenyl methane,

phenyl-bis(2,5-dimethyl-4-isocyanatophenyl)methane,

2,7-diisocyanatofiuorene,

2,6diisocyanatophenanthroquinone,

3,6-diisocyanato-9-ethylcarbazole,

3,8-diisocyanatopyrene,

2,8-diisocyanatochrysene,

2,4-diisocyanatodiphenylsulfide,

bis (4-isocyanatophenyl sulfide,

bis (4-isocyanatophenyl) sulfone,

bis(4-isocyanatobenzyl)sulfone,

2,4'-diisocyanato-4-methyldiphenylsulfone,

4-methyl-3-isocyanatobenzylsulfonyll-isocyanatophenyl ester,

4-methoxy-3-isocyanatobenzylsulfonyl-4'- isocyanatophenyl ester,

bis (2-methyl-4-iso cyanatophenyl) disulfide,

bis 3 -methyl-4-isocyanatophenyl) disulfide,

bis 4-methyl-3 -iso cyanatophenyl) disulfide,

bis(4-methoxy-3-isocyanatophenyl)disulfide,

bis 3 -methoxy-4-isocyanatophenyl disulfide,

4-methyl-3-isocyanatobenzylsulfonyl-4-isocyanato-3- methylanilide,

N,N-bis 4-isocyanatobenzylsulfonyl) -1,2-

diamonoethane,

bis 3 -rnethoxy-4-isocyanatobenzyl) sulfone,

1,2-bis (4-methoXy-3-isocyanatobenzylsulfonyl ethane,

N,N-bis(4-methoxy-3-isocyanatobenzyl) -1,2-

diamonoethane,

2,4,6-triisocyanatotoluene,,

triisocyanatomesitylene,

1,3,7-triisocyanatonaphthalene,

2,4,4'-triisocyanatodiphenylmethane,

bis (2,5 -diisocyanato-4-methylphenyl) -methane,

tris(4-isocyanatophenyl)methane,

N,N'-bis(4isocyanatophenyl)carbamyl acid chloride and the like.

The invention is further described by the examples which follow in whichall parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 Preparation of oligomer from trimethylol propane, neopentylglycol and diphenyl garbonate A -liter, 4-necked round-bottom flaskequipped with a magnetic stirrer, a thermometer, nitrogen inlet tube,

manometer, fractionating column and vacuum pump was charged with 268 g.(2 moles) of 1,1,1-trimethylol propane, 833 g. (8 moles) of neopentylglycol, 1928 g. (9 moles) of diphenyl carbonate, and 0.016 g. of LiOH-H'O. The fractionating column, constructed of glass and vacuum-jacketed,contained a section 30 inches long and 1.5 inches in diameter packedwith 316 stainless steel saddles, 0.16 X 0.16 inch having holes punchedin them. The column head was of the total reflux-total take-off type,the reflux ratio being controlled with an automatic timer. The pressureat the head was maintained constant by means of a manostat.

The charged flask was then evacuated and filled with dry nitrogen 5times. The batch temperature was raised to 150 C. by means of anelectric heating mantle at which temperature the head pressure wasadjusted with the vacuum pump and manostat to mm. of mercury. Phenol wascollected at a reflux ratio of 4/1. In 11.25 hours 1671 g. of phenol wascollected (98.6% of the theoretical value). Vapor phase chromatographicanalysis indicated a phenol purity of 99.6%. The oligomer productremoved from the flask amounting to 1283 g. was a very pale, (Gardnercolor less than 1) low melting amorphous solid which analyzed 2.56milliequivalents of hydroxyl per gram, molecular weight of about 1900and a hydroxyl functionality (number of hydroxyls per molecule) of 4.9.The column hold-up was 70 g. and was shown by vapor phasechromatographic analysis to be 68% neopentyl glycol and 32% phenol. Thestructure of this hydroxyl terminated oligomer is not definitely knownbut is presumed to have such units as:

with the penultimate member of this list predominating since theapparent nominal reaction stoichiometry is 2/ 8/ 9 trimethylolpropane/neopentyl glycol/diphenyl carbonate and the condensation processis essentially carried to completion. If the neopentyl glycol lost inthe column holdup is taken into account then this stoichiometry would be2/ 7.7/ 9 trimethylol propane/neopentyl glycol/diphenyl carbonate.

The oligomer product is soluble in toluene but not readily soluble inaliphatic alcohols although a toluene-butanol mixture can be used as adiluent. The oligomer solutions showed no tendency to crystallize out ofsolution.

EXAMPLE 2 Hexamethoxymethylmelamine cured oligomer The hydroxylterminated oligomer obtained in Example 1 was dissolved in toluene (75%solids) and then blended with hexamethoxymethylmelamine, toluene andp-toluenesulfonic acid catalyst to provide coating solutions at 65%solids. All of these solutions were clear, pale in color (less than 1 onthe Gardner color scale) and low viscosity (about 50 centipoises). Filmswere cast from these solutions with a 4 mil doctor blade on glass and onbonderized steel followed by baking at C. for 45 minutes. The impactstrength of the films which cured on the bonderized steel was measuredand recorded in Table 1.

The Gardner Impact Strength Test indicates the ability of a coating on acoated metal panel to withstand an impact from an impinging ball withoutcracking or peeling on the convex side of the indentation which resultsfrom the impact.

The 80/20 and 60/40 coatings on glass were stripped off and subjected totensile tests according to ASTM D-882 and D-256. These results are alsoshown in Table 1.

TABLE 1 Weight ratio oligomer to hexanretl1oxymethylmelanline Oligomcr,g 12. 00 10. 67 s. 00 llexainethexy1uethyln1elnmiue 1. 00 2. 00 4. 00Toluene 2. 38 2. 71 3. 38 25% p-tolueucsulfonic acid, cc 0. 0. l0 0. 10Gardner impact; strength, in.-lb 160 100 Tensile strength, p.s.i 4, S00Tensile modulus, p.s.i 230, 000 Elongation, percent 15 Impact strength,it. lb./in.

EXAMPLE 3 Diisocyanate cured oligomer The hydroxyl terminated oligomerdescribed in Example 1 was dissolved in dry toluene to afiord a solutioncontaining solids. Five 5.54 g. samples of this 70% solution were eachadmixed with one of the five diisocyanates:

1.00 g. of bis(2-isocyanatoethyl)carbonate (CDI) 1.27 g. ofbis(Z-isocyanatoethyl)furmarate (FDI) 1.60 g. ofbis(2-isocyanat0ethyl)-5-norborene-2,3-dicarboxylate (CEDI).

1.54 g. of bis(2-isocyanat0ethyl)-4-cyclohexane-l,2-dicarboxylate(CEDI).

0.87 g. of 2,4-tolylenediisocyanate (TDI) These mixtures were cast onglass and bonderized steel and cured for one hour at 150 C. All of thecured films possessed good mar resistance and outstanding toughness asevidenced by Gardner Impact strengths both normal Tensile strength,psi-2,500

Tensile modulus, p.s.i.20,000 Elongation, percent220 Impact strength,ft. 1bs./in. 65 Glass transition temperature, C.30 Modulus at 10,000p.s.i.-30 Modulus at 1,000 p.s.i.35

Modulus at p.s.i.

EXAMPLE 8 Example 1 was repeated with the exception that pentaerythritolWas substituted for the trimethylol propane and the stoichiometry of thecharge was 1/ 8/9 neopentyl glycol/pentaerythritol/diphenyl carbonate.The resultant hydroxyl terminated oligomer was a waxy solid having anhydroxyl equivalent of 2.46 milliequivalents of hydroxyl per gram andwas almost indistinguishable from the oligomer of Example 1.

EXAMPLES 9-14 When the hydroxyl terminated oligomer prepared asdescribed in Example 8 was cured with hexamethoxymethylmelamine asdescribed in Example 2 and with the diisocyanates described in Examples37, cured oligomers having similar physical properties were obtained.

EXAMPLES 1520 Hydroxyl terminated oligomers cured withhexamethylolmelamine and vinyl chloride/ vinyl acetate/vinyl alcoholterpolymer The hydroxyl terminated oligomer prepared in Example 1 wasblended with hexamethoxymethylmelamine and a vinyl chloride/ vinylacetate/vinyl alcohol 91/3 6 terpolymer (intrinsic viscosity, incyclohexanone at 30 C., 0.57) in the following ratios ofterpolymer/oligomer/hexamethoxymethylmelamine:

72/16/12, 45/40/15 and 18/64/18 in a toluene/methylisobutyl ketonesolvent at 25-42% solids content. A 0.25% p-toluenesulfonic acidcatalyst was added and films cast on glass and bonderized steel panels.The films were cured by baking one series at 100 C. for 2 hours andanother series at C. for 1 hour. In all cases very hard, mar resistant,methylisobutyl ketone insoluble films were obtained.

EXAMPLES 21-29 Preparation of hydroxyl terminated oligomers withcompositional variations Hydroxyl terminated oligomers with higher andlower hydroxyl contents and functionalities than that prepared inExample 1 were prepared from trimethylol propane (TMP), neopentyl glycol(NPG), and diphenyl carbonate (DPC). Pertinent data are presented inTable 2 together with that from Example 1. The procedure used was thatof Example 1 except that a l-liter flask was used as the reactor.

Films of these products cured with hexamethoxymethylmelamine (0.25%p-toluenesulfonic acid catalyst at C. for 45 minutes were alsoprepared). These also showed practical hardness properties which wouldallow their use as protective coatings although they differed from theproduct described in Example 2 in that Example 22 cured to a harderproduct while Examples 21 and 23 were somewhat softer.

Films of the products of Examples 21, 22 and 23 were also cured withbis(2-isocyanatoethyl)carbonate (10% excess over the calculatedstoichiometric ratio) and 0.10% dibutyl tin dilaurate as catalyst. Theproperties of the cured films were similar to those described inExamples 3-7.

TABLE 2.OLIGOI\IERS OF DIFFERENT IIYDROXYL CON- AND OF DIFFERENTIIYDROXYL 1* UNCTlON- Example number 21 22 23 1 Trimethylolnropauc, g.33. 5 134. 2 80. 5 Neopentyl glycol 234. 3 150. 2 108. 1

Diphenyl carb0uate 482. 0 482. 0 4 10. 8

LiO II. 11 0 0. 004 0. 001 0. 004

Product yield, {2 313. 7 332. 0 314. 5

Product appearance Material balance, percent 100.0 00. 6 0t). 0

I'Iydroxyl content, meq./g 1. 54 4. 12 3. 50

IIydroxy Func A. 4. O 7.0 4. 4 TMP/NPG/D PO rat 1/8. 5/!) 4/5. 8/9 2/5.8/7 2/7. 7/0 Molecular weight 731 1, 280 330 Ca. 1, 500

l Waxy solid. 2 Tacky solid.

EXAMPLES 3040 Oligomers based on other raw materials A number ofsubstitutions of raw materials for those of the Example 1 formulationwere made. These experiments are summarized in Table 3. Several diolswhich did not possess the neopentylene structure gave coatings ofcommercial interest when cured with hexamethoxymethylmelamine or with adiisocyanate although they did not possess comparable toughness.

Some diols having the neopentylene structure show much of the uniqueperformance of the Example 1 formulation. These included the next higherhomolog of NPG, 2-methyl-3-ethy1-propanediol-1,3 and Ester-Diol whichhas the structure:

Exp. Mole OH No. Replacement chemical ratio 1 Appearance value Coatingcharacteristics on curing Replacements for neopentyl glycol:

30 Dipropylene glycol 2/8/9 Visc. liquid g 31.. Pentanediol-l,5 2/8/9.do All of these oligomers can be cured to hard coatings. 32.. Ethyleneglycol.

33 Ester-diol 204 34 do 35.. 2-methyl-2-ethylpropanediol-1,3.

36. 1,4-cyelohcxanedimethanol 2/8/9 .do 37" 2,2,4trimethylpentandiol-1,32/8/9 Thin liquid 38. 2-ethy1-2-nitropropanediol-l,3. 2/8/9 Replacementsfor trimethylolpropane:

39.. Pentaerythritol 1/8/9 Waxy solid 40.. Hexanetriol-1,2,6 2/8/9Liquid }Have much of the cure behavior of Example 1 formulation.

Does not cure well with hexamethoxymethylmclamine but acts as though itdecomposes. N itro compound decomposed during preparation 2. 46 Cureslike Example 1 formulation. 2.08 Low viscosity liquid does not cure wellwith hexamethoxymethylmelamine.

1 Mole ratio of polyol/diol/diphenylcarbonate charged; product ratio maybe slightly different.

Pcntaerythritol gave a product which appeared to be indistinguishablefrom the Example 1 product. Hexanetriol-l,2,6, an isomer of TMP, gave anabnormal product, a low viscosity liquid which did not cure Well.

EXAMPLES 41-42 Carbonate oligomers of TMP/Ester-Diol Table 4 shows twooligomers based on the Ester-Diol depicted in Examples 3040, one a molarsubstitution variation on Example 1, and the other adjusted to obtainthe hydroxyl content of Example 1 as well as its hydroxyl functionality.Both products were made in three-necked flasks equipped with magneticagitation, thermometer, and a Vigreux column surmounted with adistillation head permitting reflux control, condenser, receiver, etc.Initial distillation of lay-product phenol was at 100 mm. absolutepressure; toward the end the pressure was reduced to about mm. When thetheoretical quantity of phenol had been collected, the distillation ofvolatiles simply ceased; apparently there is little, if any, tendency,even in the presence of a modest amount of hydroxyl, for ester exchangereactions leading to the generation of neopentyl glycol.

TABLE 4.CARBONATE OLIGOMERS (1)113 TRIMETHYLOL PROPANE AND ESTER-BIOExample 41 42 Molar ratio TMP/E-D 204/DPG 2/3. 7/5 2/4. 4/5. 7Trimethylolpropane, g 188 268 Ester-diol 204 529 898 Diphenyl carbonate.750 1, 220 LiOPLHzO 0. 008 0. 012 Reaction temperature C 165-200 17l-204Reaction time hrs 4. 5 4. 5 Distillate yield (theory) g 658 (659) l 1,084 (1, 061) Product yield (theory) 804 (808) 1, 296 (1, 325) Materialbalance percen 99. 6 99. 7 Appearance I-Iydroxyl content (theory) 2. 76(2. 95) 2 52 (2. 57) Hydroxyl functionality. 4. 86 4. 86 Molecularweight (theory 1, 283 (1, 965) (1, 970) 1 The high distillate yield wasthe result of some flooding in the initial stage of the phenoldistillation.

2 Pale bal am.

Polyester oligomer preparations In a further study of coatings resinsbased on the Ester-Diol this diol was esterified with various cyclicdibasic acids and a minor amount of trimethylol propane to yieldbranched, hydroxyl-terminated, low molecular Weight polyesters. Thecyclic acids used included phthalic, isophthalic, tetrahydrophthalic andhexahydrophthalic. In addition, a few experiments were made withpropylene glycol and neopentyl glycol in place of Ester-Diol. Cur ingthese polyesters with a melamine resin or with a diisocyanate gave somevery attractive coatings.

The several polyesters made for curing with diisocyanates or withhexamethoxymethylmelamine are summarized in Table 5. To make comparisonsmore meaningful each of the polyester formulations was designed so thatthe average polyester molecule would contain 4.9 terminal hydroxyls at astandardized weight per hydroxyl of 400 grams (that is, a hydroxylconcentration of 2.50 meq./ g.). With the exception of propylene glycol,which is somewhat volatile (and difficult to compensate for losses), theseveral polyesters of Table 5 met this requirement.

Each of the polyesters of Table 5 was made by an azeotropic distillationtechnique, the weights of reactants shown being for a 2-liter flask.Enough xylene was added to obtain a good reflux rate at about 200 C.,byproduct Water being removed and xylene returned via a Dean- Starktrap. Because it was convenient to do so, each batch was held overnightat reflux to obtain a low acid value product. The polyester was thenreduced to 75% nonvolatile with toluene.

TABLE 5.-PREPARATION AND PROPERTIES OF HYDROXYL-TERMINATED POLYESTERSExp No. Diacid used Diol used TMP, g. Diol, g. Acid, g. Molar ratio 1Acidity 2 Hydroxyl 2 Viscosity 3 Color 3 43., Phthalic Est er-diol 268552 592 2/2. 7/ 4 0. 09 2. 43 Z3-Z4 3 44 Isophthalic. ..do 268 552 5922/2. 7/4 0. 20 2. 53 Z6-Z7 4 268 552 592 2/ 2. 7/4 0. 16 2. 6 4-5 45Tetrahydrophthalic do 268 552 609 2/2. 7/4 0. 14 2. 63 Zi-Z2 1 46--.Hexahydrophthalic .do 268 552 617 2/2. 7/4 0. 16 2. 50 Z3 1 47 PhthalicPropylene glycol. 268 368 889 2/4. 7/6 0. 03 2. 27 Z7 2-3 48Tetrahydrcphthalic do 268 321 821 2/4. 1/5. 4 0. 14 2. 8 1 49 .doNeopentyl glycoL- 268 385 761 2/3. 7/5 0. 15 2 49 Z4 1 1Trimethylolpropane/diol/diacid.

2 Both acidity and hydroxyl values are in units of milliequivalents/gramsolids basis; to convert to mg. KOH/g., multiply by 56.1. B othviscosity and color are in Gardner units, measured at solids (toluene).

1 1 EXAMPLES 50-56 Melaminue-cured polyester oligomer coatings Thepolyester oligomers described in Examples 43-49 were cured at anoligomer/hexamethoxymethylmelamine ratio of about 80/20 by weight, usingp-toluenesulfonic acid, 0.25% by weight based on total solids, as thecuring catalyst:

75% polyester solution g 10.67 Cymel 300 2.00 Toluene 2.73 25%p-toluenesulfonic acid in n-butanol cc 0.10

These solutions had a moderately low viscosity (not measured) andhandled nicely when used with a doctor blade to cast films on glass ormetal. On curing 45 minutes at 150 C., they were converted to very hard,very mar resistant, MEK-insoluble coatings; on bonderized steel thesepassed a 40 inch-pound impact. Differences among the several polyesterfilms were slight.

EXAMPLES 57-63 Diisocyanate-cured coatings A calculated excess ofdiisocyanate was used to cure each of the Example 43-49hydroxyl-terminated polyesters, for example:

75 (TMP/Ester-Diol/Tetrahydrophthalic acid) g 5.08 CDI 1.10

Toluene 3.84 1% Dibutyl tin dilaurate in toluene cc 0.50

Each was reduced to 50% nonvolatile in dry toluene and the tin catalyst(0.10% by weight) added just before using the solution. The working timewas about an hour at room temperature.

Air-dried films were dry to touch in about 2 hours. At 24 hours, theair-dried films had a rather good degree of through-cure and a modestlygood surface hardness; such films on bonderized steel have passed a 120inchpound impact. The same level of cure can also be realized wtih anhour bake at 100 C.

EXAMPLES 64-65 Samples of hydroxyl terminated polyester oligomerprepared in Example l and of the oligomer cured withhexamethoxymethylmelamine and bis(2-isocyanatoethyl) carbonate weresubjected to ultraviolet absorption analysis. The oligomer was found tobe essentially transparent in the near ultraviolet with slightabsorption at 230, 272, 278 and 288 millimicrons due to traces of phenolintroduced in its preparation. The oligomer cured withbis(2-isocyanatoethyl)carbonate was essentially transparent in the nearultraviolet. The hexamethoxymethylmelamine resin absorbed strongly below300 my but not above.

Although this invention has been described in its preferred forms with acertain degree of particularity, it is understood that the presentdisclosure of the preferred forms has been made only by Way of example,and that numerous changes may be resorted to without departing from thespirit and scope of the invention.

What is claimed is:

1. A cured hydroxyl terminated oligomer obtained by heating a mixtureof:

(a) 1 mole of a polyol selected from the group con- 12 sisting of1,1,1-trimethylolpropane and pentaerythritol;

(b) 1.35 to 2.2 moles of ester-diol having the formula:

R R l1OCHz( COzOII2-( J-CH2OII wherein each of R and R is an alkyl grouphaving up to 4 carbon atoms; and

(c) 2 to 2.85 moles of an ester-forming compound se lected from thegroup consisting of cyclic dibasic acids and cyclic anhydrides, at atemperature of about 150 to 250 C. for at least 2 hours; said oligomerthereafter being cured by reacting with at least a stoichiometric amountof an organic polyisocyanate in an organic solvent at ambienttemperatures, removing solvent, and thereafter air-drying at ambienttemperatures to about 100 C. until hard.

2. The cured oligomer claimed in claim 1 wherein the polyisocyanate is adiisocyanate.

3. The cured oligomer claimed in claim 2 wherein the diisocyanate is2,4-tolylenediisocyanate.

4. The cured oligomer claimed in claim 2 wherein the diisocyanate isbis(2-isocyanatoethyl)carbonate.

5. The cured oligomer claimed in claim 2 wherein the diisocyanate isbis(2-isocyanatoethyl)-4-cyclohexene-1,2- dicarboxylate.

6. The cured oligomer claimed in claim 2 wherein the diisocyanate isbis(isocyanatoethyl)fumarate.

7. The cured oligomer claimed in claim 2 wherein the diisocyanate isbis(Z-isocyanatoethyl)-l,4,5,6,7,7hexachloro-S-norbornene-2,3-dicarboxy1ate.

8. The cured oligomer claimed in claim 2 wherein the diisocyanate ismethylene bis(4-phenyl isocyanate).

9. The cured oligomer claimed in claim 2 wherein the diisocyanate isbis(2 isocyanatoethyl)-5-norbornene-2,3- dicarboxylate.

References Cited UNITED STATES PATENTS 2,970,118 1/1961 Wilson et al.2602.5 2,981,700 4/1961 Parker et al. 26025 2,982,754 5/1961 Shetfer etal. 260--33.4 3,015,650 1/1962 Schollenberger 260 3,055,869 9/1962Wilson et al. 26075 3,079,350 2/1963 Bernstein 2602.5 3,094,510 6/1963Parker et al. 26075 3,141,900 7/1964 Lynn et al 260453 3,158,638 11/1964Hoch 260455 3,288,730 11/1966 Baltes et al. 2602.5 3,322,812 5/1967Brotherton et al 260463 3,352,830 11/1967 Schmitt et al. 26077.53,373,143 3/1968 Chilvers et al. 26075 3,248,373 4/1966 Barringer26077.5

FOREIGN PATENTS 635,304 11/1963 Belgium.

OTHER REFERENCES Condensed Chemical Dictionary, 7th edition Reinhold,New York (1966) p. 692.

DONALD E. CZAJA, Primary Examiner H. S. COCKERAM, Assistant ExaminerU.S. Cl. X.R. 26067.6, 850'

